The cardinal number that is the sum of three and one

In mathematics, the quaternion number system extends the complex numbers.

Unit quaternions, known as versors, provide a convenient mathematical notation for representing spatial orientations and rotations of elements in three dimensional space.

In mathematics, a quaternion algebra over a field F is a central simple algebra A over F that has dimension 4 over F. Every quaternion algebra becomes a matrix algebra by extending scalars, i.e. for a suitable field extension K of F, A ⊗ F K {\displaystyle A\otimes _{F}K} is isomorphic to the 2×2 matrix algebra over K. The notion of a quaternion algebra can be seen as a generalization of Hamilton's quaternions to an arbitrary base field.

In bookbinding, a section, gathering, or signature is a group of sheets folded in half, to be worked into the binding as a unit.

Quaternion is a poetry style in which the theme is divided into four parts.